- Benzofuran Derivatives. Part 4. Synthesis of Benzofurans and 2,3,4,5-Tetrahydro-1-benzoxepin-3,5-diones
-
By treatment of ethyl 4- or 5-substituted 2-acetylphenoxyacetates 1 with potassium hydroxide in dry dioxane, benzofurans 2-7 and 2,3,4,5-tetrahydro-1-benzoxepin-3,5-diones 8 were obtained.The relative yields of benzofurans 2-7 and 2,3,4,5-tetrahydro-1-benzoxepin-3,5-diones 8 varied with the types of 4- or 5-substituents.The electron-donating 4-methoxyl group favored the formation of benzoxepins.On the other hand, electron-withdrawing substituents such as the 4-nitro group favored the formation of benzofurans.When esters 1 were treated with sodium amide,2,3-dihydrobenzofurans 2 were obtained exclusively regardless of 4- or 5-substituents.
- Suzuki, Tsuneo,Tanemura, Kiyoshi,Horaguchi, Takaaki,Shimimizu, Takahachi,Sakakibara, Tohru
-
p. 423 - 429
(2007/10/02)
-
- BENZOFURAN DERIVATIVES. I. ON THE EFFECTS OF SUBSTITUENTS IN BENZOFURAN SYNTHESES.
-
The Roessing's reaction of 4-substituted 2-acylphenoxyacetic acids give a mixture of benzofurans and 2-benzofurancarboxylic acids. The relative yields of benzofurans and 2-benzofurancarboxylic acids depend on the substituents on the benzene ring of the 2-acylphenoxyacetic acids. Electron-withdrawing substituents such as nitro groups favor the formation of 2-benzofurancarboxylic acids. On the other hand, the formation of benzofurans is favored by the steric hindrance of 2-acyl groups in the reaction of 2-acyl-4-nitrophenoxyacetic acids with anhydrous sodium acetate and acetic anhydride.
- Suzuki,Horaguchi,Shimizu,Abe
-
p. 2762 - 2767
(2007/10/02)
-
- Thermal Rearrangement of 2-Methyl-2-(2'-acetoxy-5'-methylphenyl)oxirane
-
Thermal rearrangement of 2-methyl-(2'-acetoxy-5'-methylphenyl)oxirane (2) at 160 deg C for 1 hr furnishes a mixture of 2-(2'-hydroxy-5'-methylphenyl)propenyl acetate (4), 3,5-dimethylbenzofuran (11), 2-(2'-acetoxy-5'-methylphenyl)-propenyl acetate (5), 2-hydroxy-5-methylacetophenone (13), (+/-)-2,3-dihydro-3α,5-dimethylbenzofuran-2β-ol (14) and (+/-)-2,3-dihydro-3β,5-dimethylbenzofuran-2β-ol (15).Evidences in support of E-geometry at the ethylenic linkage of enolester (4) are presented.Treatment of 4 with alkali in the presence of air furnishes 13.Oxidation of a mixture of 14 and 15 gives 2,3-dihydro-3,5-dimethylbenzofuran-2-one (19). 3,5-Dimethylbenzofuran (11) has been prepared from 4.Thermal rearrangement of 2-methyl-(2'-acetoxy-5'-bromophenyl)oxirane (27) furnishes 5-bromo-3-methylbenzofuran (12) in good yield.
- Dhekne, Vijay V.,Rao, A. S.
-
p. 852 - 855
(2007/10/02)
-
